Bicycle MechanicsBroken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

I picked up a used Trail-A-Bike. The seatpost collar that came with it is for a 27.2 seatpost. Should I get a shim to make up the gap or is collar with a shim inside too many seperate loose items? Or is it necessary to get a single shim/collar to safely cover the entire gap-it looks like the diameter might be 30+mm on without the existing collar.

My best mountain bike and best road bike each use a 27.2, but I'd rather user lesser quality bikes when towing.

I'm assuming you have an Adams. You should have the correct shim, or else it will wobble excessively. You can order a shim kit from a bike shop or online retailer. The hack way is to cut the existing shim. You'll need a vise and hacksaw to do this, and patience, as you cut the shim longways.

While you're at it, tighten down the two bolts at the universal joint to stop wobbling.